In commercial nuclear reactors, it is necessary to periodically monitor the axial flux distribution as directly as possible throughout the core in order to perform proper fuel management as well as to monitor other conditions such as the rod position indication and the fixed in-core system. This task is presently performed by a movable in-core flux mapping system requiring substantial operator interaction for control and data reduction.
While numerous different detection techniques have been employed in the past, the control of the movable in-core detectors has generally fallen into one of two categories. For simple systems not requiring coordinated automatic control and data reduction of multiple detectors, individual control systems are provided for each drive mechanism and data reduction is generally a task left to the operator or a central plant computer. While this approach produces a degree of fault tolerance since a failure of one control system will not affect the others, this approach usually places a heavy burden on the plant computer. The operating personnel are burdened with detailed data reduction and control responsibility.
For automated systems, in which multiple detectors need to be controlled and their data reduced internally in a coordinated manner, a centralized data processing and control technique is usually employed to reduce the cost. Unfortunately, these systems are vulnerable to numerous single failures that can prevent or delay a flux map with a resulting penalty in plant performance. Fully redundant systems have also been considered but generally are not used due to excessive costs.
Thus, there is a strong need to provide an economical, fully automated, movable in-core flux mapping system with coordinated control of multiple detectors and internal data reduction as well as tolerance to single random device failures.